Disc brake boot seals are known. However, because the boot seal must be in its collapsed condition when the piston of the disc brake system is installed (to provide sufficient room for the piston between the top of the boot seal and the top of the caliper), such known boot seals are presently molded in their collapsed condition. This process is expensive and there is high mold breakage. The seal that is presently used includes a boot or sleeve having a uniformly thin flexible wall molded in an accordion-pleated, bellows, or collapsed condition. During operation, the known boot seal can stretch into an elongated condition. One end of the boot seal is retained in a cylinder bore recess. In the interest of space and weight economy, the piston-to-bore annular space must be kept as narrow as possible. For example, the piston can have an outside diameter of 45 mm and the cylinder recess or bore for retaining the boot can have a 58.3 mm bore diameter. The boot seal must be capable of extending approximately 30 mm and collapsing to an overall height of about 11.5 mm when the piston is retracted to change the brake pads. The resulting narrowness of the annular space between the retaining wall of the bore and the piston makes it very difficult to mold a boot seal of bellows configuration with its accordion-like convolutions having sharp bends. The convolutions are required to permit the conventional boot seal to flex and roll into the annular space upon retracting the piston. The sharp bends in the bellows wall of the prior art boot cause the boot to operate in an uneven, jerky manner during retraction and extension. A conventional type of convoluted boot having a bellows type sleeve is described, for example, in U.S. Pat. No. 3,998,466. It has also been suggested to mold the boot seal in its extended condition, however, such seal does not remain in its collapsed condition, but rather self-extends and thus it must be held in its collapsed condition during assembly of the brake system, and particularly during assembly of the brake piston with the rest of the brake system, see U.S. patent application Ser. No. 875,765, filed Feb. 7th, 1978 by Dean R. Bainard & Martin E. Benjamin, now abandoned.
It is an object of the present invention to provide a disc brake boot seal (and method) that can be molded in its extended condition and then collapsed and that will releasably stay in its collapsed condition without self-extending so that the disc brake system can be more readily and easily assembled, for example, without having to hold the boot seal in its collapsed condition.
It is another object of this invention to overcome the problems in the prior art, such as the expense and high mold breakage inherent in molding the boot seal in its collapsed or convoluted condition.
It is another object of the present invention to provide a collapsible sleeve that can be molded in its extended condition and that has a plurality of walls including certain ones that interact to releasably hold, lock or maintain the sleeve in its collapsed condition.